It is becoming popular and, in many cases, legally necessary to market food and pharmaceuticals in containers which give physical evidence of tampering; i.e., containers having a frangible section which typically must be broken or disassembled in some significant fashion before they may be opened to provide access to the contents.
Molded plastic containers are among the most popular types of containers for food products and pharmaceuticals and the tamper-evident feature is typically provided by means of a pre-located tear strip which is attached to the closure or container by means of a frangible section. Once the tear strip is removed, one may easily remove and replace the closure.
Examples of tamper-evident closures having frangible and tear strips in both metal and plastic are illustrated by the U.S. Pat. Nos. 4,520,942, 4,487,329 and 4,476,993. U.S. Pat. No. 4,024,976 granted May 24, 1977 to Daniel Acton on an invention entitled "Tamperproof Molded Package" discloses a single level security system wherein a tear strip formed integrally with the container covers just the lower edge of the closure skirt to impede removal of the closure from the container. Once the tear strip is removed, the closure is easily removed by lifting an edge and there is no security at all; i.e., no second tamper-evident function.